Preparation of a jet fuel



March 17., 1964 Filed Dec. 29, 1959 United States Patent 3,125,503PREPARATIGN F A JET FUEL Edwin Robert Kerr, Fishkill, Edward R.Christensen,

Wappingers Falls, William F. Franz, Hopewell Junetion, and Herbert E.Vermilion, Wappingers Falls, N.Y., assiguors to Texaco Inc., New York,N.Y., a corporation of Delaware Filed Dec. 29, 1959, Ser. No. 862,592Claims. (Cl. 208-79) This invention relates to the production of gasturbine engine fuels. More particularly, it relates to the production offuels suitable for use in jet aircraft engines. In one specicembodiment, the present invention is concerned with the simultaneousproduction of hig'n octane fuel for piston engines and high luminometernumber fuels for jet engines.

Fuels currently in use for the propulsion of jet aircraft, as gasturbine powered aircraft are commonly called, are kerosene, JP-4 andLIP-5, the last two being military specifications (MIL-F-5624C amend.1). While these fuels are satisfactory to the extent that they performthe desired functions, there are several disadvantages attached to theiruse in gas turbine powered aircraft.

One of the disadvantages of the fuels currently in use is that theyproduce excessive smoke during take-off. When jet fuels prepared by theprocess of the present invention are used under the same conditions, theproblem of excessive smoke during take-off is substantially eliminated.

Another disadvantage attached to the use of current jet engine fuels isthe necessity for frequent engine overhauls. In the operation of a gasturbine engine, atmospheric air is compressed and is then introducedinto the combustion section where it is heated by burning fuel therein.The hot gases are then expanded through a turbine and exhausted to theatmosphere through a jet or tailpipe. The combustion takes place in acombustion chamber into which a portion of the compressed air, sometimescalled the primary air, is mixed with a fuel spray in approximately thestoichiometric ratio to support combustion and the balance of the air,sometimes called secondary air, is introduced into the hot combustiongases to cool them to a temperature which can be tolerated by thedownstream parts including the turbine inlet nozzles and blading. Thecombustion zone is surrounded by a metallic liner or flame tube. Theliner is subjected to considerable thermal stress and generally when thefuels currently in use are employed in the gas turbine engine the linerwhich surrounds a liame of 30007 F. or higher is subjected to extremestress principally due to radiation from the flame which results increeping, warping and buckling of the part. In some instances the highradiation from the flame also causes buckling of the turbine rotor tosuch an extent that malfunctioning and sometimes complete failure of theengine results. For this rea-son, it is customary to inspect jetaircraft engines frequently and experience has shown that a fairlythorough overhaul is necessary after about 500-600 hours of operation.

It is an object of the present invention to provide a iet engine fuel ofimproved burning characteristics. Another object of the presentinvention is to provide a jet fuel of low aromatic hydrocarbon content.Another object of the present invention is to produce a jet fuel whichburns with a flame of low luminosity. Another object of the presentinvention is to produce a gas turbine engine fuel which subjects theengine parts to reduced thermal stress. Another object of the presentinvention is to provide a process for the separate production of a3,l25,503 Patented Mai'. 17, 1964 motor fuel of high octane number and ajet fuel of high luminometer number.

The luminometer number is a measure of the burning characteristics of afuel, the higher the luminometer numer the less smoke produced by thefuel during take-off and the lower the amount of radiation produced bythe flame. The luminometer number may be determined using a Smoke PointLamp described in the Tentative Method of Test for Smoke Point of letFuels, ASTM Designation Dl322-54T* modified by the addition of ltwothermocouples, one for measuring the temperature of the incoming air,the other shielded from the iiarne and inserted in the chimney tomeasure the temperature of the combustion gases, and a radiometeradjustably positioned to measure the amount of radiation emanating fromthe iiame.

To determine the luminometcr number, several determinations are madeburning tetralin in the lamp, each run being made at a different wickheight, the radiometer being positioned at the zone of maximumradiation, and the amount of radiation for each run and the temperaturedifferential between the incoming air and the combustion gases beingrecorded. After several runs have been made on tetralin, a curve isdrawn plotting AT against the amount of radiation. Similar curves arethen made for isooctane and the test fuel. The AT for each material at aselected amount of radiation, e.g. 0.3 mv., is, read from the curves andis inserted in the formula:

AT (test fueD-AT (tetralin) In this way the luminorneter number of thetest fuel can be determined.

It has been found that fuels having low luminometer numbers burn with ahighly radiant tiame and also produce excessive smoke during take-Gif.it has also been found that fuels having relatively high aromaticcontents have relatively low luminometer numbers. Even fuels which meetcurrent military jet fuel specifications have the undesirablecharacteristics of producing excessive smoke during take-off and ofburning with names of high radiation which are detrimental to the lifeof the jet engine. For example, the specifications for JP-4 and JP-Spermit a maximum aromatic content of 25%. However, jet fuels which meetthis requirement are unsatisfactory in the two respects just mentionedprobabiy for the reason that they generally contain more than 10%aromatica ln accordance with one embodiment of the present invention, acrude oil is separated into a naphtha fraction and a heavy fractionhaving a boiling range of from about 390 to 760 F. The naphtha issubjected to catalytic reforming to convert the naphthenes present toaromatics which are removed from the reformate by solvent extraction.The heavy fraction is subjected to catalytic cracking and the product isseparated into a C2 and lighter gaseous fraction, a CS-C., olefincontaining fraction, a (S5-400 F. fraction and a 400 R+ fraction whichis recycled to the catalytic cracking operation. The C2 and lighterfraction is removed from the system. The C5- 400 F. fraction may beprocessed further as, for example, by catalytic reforming or it may beseparated into a C-Cq fraction which is isomerized and the balancereformed or it may be combined in its entirety with the aromatic extractrecovered from the reformate. The C3C4 olefin containing fraction issubjected to a polymerization reaction and the resulting liquid polymertogether with the non-aromatic portion of the reformate is hydro- *ASTMStandards on Petroleum Products and Lubricants, published 1956 by theAmerican `Society for Testing Materials.

i3 genated to produce a jet fuel of improved burning characteristics.

The reforming is ordinarily conducted in the presence of a reformingcatalyst, such as a platinum on alumina catalyst which may or may notcontain combined halogen. Molybdena-alumina catalysts are alsosatisfactory for this purpose. The reforming is conducted at atemperature of from about S50-950 F. and a pressure of about 500p.s.i.g. Hydrogen is recycled at the rate of about 8000 cubic feet perbarrel of liquid feed. The reformate, i.e., the normally liquid productrecovered from the reforming reaction is then subjected to a treatmentwhich separates the aromatic constituents from the paraffinicconstituents. This may be effected by treatment with a solid adsorbentsuch as silica gel or the separation may be effected by the use of aselective solvent such as SO2, furfural, ethylene glycol, diethyleneglycol, triethylene glycol or mixtures of glycols. Preferably, theseparation is effected by the use of a glycol solvent.

The S90-760 F. fraction is preferably contacted with a fluidized bed ofsilica-alumina or silica-magnesia catalyst at a temperature betweenabout 880 and 980 F. and a pressure between about and 18 p.s.i.g. Spacevelocities will range from 1.0-3.0 weight of feed per hour per weight ofcatalyst with a catalyst to oil ratio of 8-12/ 1.

The C3-C4 olefin containing fraction recovered from the cracking zoneeffluent is then contacted with an acidic polymerization catalyst suchas copper pyrophosphate, boron fluoride, aluminum chloride or phosphoricacid supported on an inert material such as quartz or kieselguhr. Thepolymerization, when a phosphorus-containing catalyst is used, isgenerally conducted at a temperature between about 300 and 500 F., apressure between 150 and 1500 p.s.i.g. The liquid polymer is thencombined with the non-aromatic portion of the reformate and the combinedstream is subjected to hydrogenation for the saturation of the polymerand also to convert residual aromatics present in the non-aromaticportion of the reformate to naphthenes.

Ordinarily, the hydrogenation is conducted in the presence of ahydrogenation catalyst. Suitable hydrogenation catalysts are platinum,palladium and nickel and the oxides or sulfides of metals such asmolybdenum, chromium, cobalt and tungsten. These catalytic materials maybe supported on materials such as alumina, silica-alumina, kieselguhrand the like. Since platinum, palladium and nickel are sensitive tosulfur compounds which may be present in the feed, it is advisable whenit contains a substantial amount of sulfur to pretreat the feed prior tosubjecting it to contact with theplatinum, palladium or nickel catalyst.A suitable treatment comprises contacting the feed with a cobaltmolybdate on alumina or a nickel tungsten sulfide catlayst in thepresence of hydrogen at a temperature ranging from about 400 F. to 900F., preferably 500 F. to 800 F. and a pressure of about 100 p.s.i.g. to1000 p.s.i.g., preferably 200-750 p.s.i.g.

Hydrogenation of the aromatics to naphthenes should be carried out at atemperature of not more than 700 F. Preferred temperatures range from500 to about 675 F. When the reaction temperature exceeds 700 F., thereaction reverses and instead of the desired hydrogenation of aromaticsto naphthenes taking place, the naphthenes present are dehydrogenated toaromatics. Pressures should he maintained above 250 p.s.i.g., preferredoperating pressures being 250-750 p.s.i.g. Space velocities may rangefrom about 0.2 to 10 volumes of feed per volume of catalyst per hour, apreferred range being from 0.5 to 4 v./v./hr. Hydrogen rates of 1000 to20,000 s.c.f./bbl. may be used although rates of 5000 to 15,000s.c.f./bbl. are preferred.

The invention may be better understood by reference to the attacheddrawing which shows diagrammatically a flow scheme for the practice ofone embodiment of the present invention and in connection with which aspecific example is described.

A crude oil is introduced through line 11 into fractionator 12 where itis separated into a normally gaseous portion withdrawn through line 13,a C5-390" F. fraction withdrawn through line 14, a 390-760 F. fractionwithdrawn through line 15 and a residual fraction withdrawn through line16. Although this separation is indicated as taking place in one vessel,it will be obvious to those skilled in the art that the separation isactually made serially in two vessels, the first operated at atmosphericpressure and the second at subatmospheric pressure.

The C5-390 F. fraction is contacted in reactor 20 with a platinumalumina combined halogen catalyst at a temperature of 900 F., a pressureof 500 p.s.i.g., a space velocity of 3.0 volumes of feed per volume ofcatalyst per hour and a hydrogen recycle rate of 10,000 cubic feet perbarrel. The reaction products are then transferred to separation zone 22through line 21. In separation zone 22 hydrogen is removed from theproduct stream and is recycled to reforming zone 20 through lines 23 and14. The normally liquid portion of the reformate is then sent toextraction zone 24 through line 25 in which zone it is countercurrentlycontacted with a glycol solvent introduced through line 30. The aromaticcontaining extract is removed from extraction zone 24 through line 31and is introduced into fractionation zone 32 where the aromatic richextract is separated from the solvent and removed as overhead throughline 33. The essentially aromatic free solvent is removed fromfractionation zone 32 and recycled to extraction zone 24 through line30. The low aromatic raffinate which contains about paraflins and smallamounts of olens, naphthenes and aromatics is removed from extractionzone 24 through line 35. Before being subjected to further treatment,the ranate is advantageously contacted in a vessel (not shown) with, forexample, water, to remove residual amounts of solvent which may bepresent.

The 390-760 F. fraction is introduced into catalytic cracking zone 40wherein it is contacted with a iluidized bed of silica-alumina catalystat a temperature of 925 F. and a pressure of 15 p.s.i.g. The spacevelocity is 2.2 weight of feed per hour per weight of catalyst and thecatalyst to oil ratio is 9.5. The reaction products are sent fromcatalytic cracking zone 40 through line 41 to fractionation zone 42 fromwhich gaseous material up through C4 hydrocarbons is removed throughline 43, a C5-400" F. fraction is removed through line 44 and the 400F.{ fraction is recycled to catalytic cracking zone 40 through lines 45and 15. Excess recycle is withdrawn from the system through line 46. TheC5-400 F. fraction is combined with the aromatic rich extract in line33.

The C4 and lighter fraction is then sent through line 43 to separationzone 50 from which C2 and lighter material is removed through line 51.The C3C4 fraction is transferred via line 52 to polymerization zone 53where it is contacted with a phosphoric acid on kieselguhr catalyst at atemperature of 420 F., a pressure of 700 p.s.i.g. and a space velocityof 0.25 liquid gallon of feed per hour per pound of catalyst. Effluentfrom polymerization reactor 53 is passed through line 54 to fractionatorS5 from which gaseous material is removed through line 60. If desired,gaseous material may be recycled through lines 61 and 52 topolymerization reactor 53 but in this example it is withdrawn from thesystem in its entirety. The normally liquid polymer is withdrawn fromfractionator 5S through line 62 where it is combined with the lowaromatic portion of the reformate withdrawn from extractor 24 throughline 35. The combined stream is introduced into hydrogenation zone 63Where it is contacted with a nickel oxide on kieselguhr catalyst at atemperature of 500 F., a pressure of 750 p.s.i.g., a space velocity of1.0 volume of feed per hour per volume of i catalyst and a hydrogen feedrate of 12,000 cubic feet per barrel of feed. The effluent fromhydrogenation zone 63 passes through line 64 to separator 6 in whichhydrogen-containing gas is removed from the etiluent and recycled tohydrogenation zone 63 through lines 67 and 62. Normally liquidhydrogenation product is then sent through line 70 to fractionator '71where it is separated into a fraction boiling below 200 F. and afraction boiling above 200 F., the lighter fraction being combined bymeans of line 72 with the extract and cracked gasoline in line 33 toyield a motor fuel having an ASTM Research Octane Number of 91 clear, 97leaded. The heavier fraction withdrawn through line 73 has a luminometernumber of 120 and is admirably suited for use alone or in combinationwith other materials as a jet fuel.

Obviously many modifications and variations of the invention ashereinbefore set forth may be made without departing from the spirit andscope thereof and therefore only such limitations should be imposed asare indicated in the appended claims.

We claim:

1, A process for the production of an improved jet fuel which comprisesfractionating a crude petroleum into a first liquid fraction having adistillation end point of about 390 F. and a second liquid fractionboiling within the range of about 390-760 F., reforming said firstliquid fraction to produce a reformate of increased aromatic content,separating said reformate into a portion rich in aromatics and anon-aromatic portion, contacting said second liquid fraction with acracking catalyst under cracking conditions to produce a crackedproduct, separating the cracked product into a Cs-C., olen-containingfraction and a cracked naphtha fraction, subjecting said C3-C4olefin-containing fraction to polymerization conditions in the presenceof a polymerization catalyst to produce a normally liquid polymer,combining said normally liquid polymer and said non-aromatic portion,contacting the combined stream with a hydrogenation catalyst in thepresence of 5,000-15,000 s.c.f. hydrogen per barrel under saturationconditions and recovering a hydrocarbon fraction boiling in the jet fuelrange from the hydrogenation product.

2. The process of claim 1, in which the cracked naphtha is combined withthe rst liquid fraction and the combined stream is reformed.

3. A process for the production of an improved jet fuel and thesimultaneous production of a high octane motor fuel which comprisesfractionating a crude petroleum into a first liquid fraction having adistillation end point of about 390 F. and a second liquid fractionboiling within the range of about 390-760" F., reforming said firstliquid fraction to produce a reformate of increased aromatic content,separating said reformate into a portion rich in aromatics and anon-aromatic portion, contacting said second liquid fraction with acracking catalyst under cracking conditions to produce a crackedproduct, separating the cracked product into a CVC., olefin-containingfraction and a cracked naphtha fraction, subjecting said (2g-C4olefin-containing fraction to polymerization conditions in the presenceof a polymerization catalyst to produce a normally liquid polymer,combining said normally liquid polymer and said non-aromatic portion,contacting theV combined stream with a hydrogenation catalyst in thepresence of 5,000-l5,000 s.c.f. hydrogen per barrel under saturationconditions and recovering a hydrocarbon fraction boiling in the jet fuelrange from the hydrogenation product, and combining 0 the crackednaphtha with the portion of increased aromatic content to produce a highoctane motor fuel.

4. A process for the production of an improved jet fuel and thesimultaneous production of a high octane motor fuel which comprisesfractionating a crude petroleum into a first liquid fraction having adistillation end point of about 390 F. and a second liquid fractionboiling within the range of about 390-760 F., reforming said firstliquid fraction to produce a reformate of increased aromatic content,separating said reformate into a portion rich in aromatics and anon-aromatic portion, contacting said second liquid fraction with acracking catalyst under cracking conditions to produce a crackedproduct, separating the cracked product into a C3-C4 olefin-containingfraction and a cracked naphtha fraction, subjecting said (2a-C4olefin-containing fraction to polymerization conditions in the presenceof a polymerization catalyst to produce a normally liquid polymer,combining said normally liquid polymer and said non-aromatic portion,contacting the combined stream with a hydrogenation catalyst in thepresence of 5,000-15,000 s.c.f. hydrogen per barrel under saturationconditions, fractionating the liydrogenation product into a liquidfraction boiling below about 200 F. and a fraction boiling in the jetfuel range and combining said fraction boiling below about 200 F., saidcracked naphtha and said fraction rich in aromatics to produce a motorfuel of high octane number.

5. A process for the production of an improved jet fuel and thesimultaneous production of a high octane motor fuel which comprisesfractionating a crude petroleum into a first liquid fraction having adistillation end point of about 390 F. and a second liquid fractionboiling within the range of about 390-760" F., reforming said firstliquid fraction to produce a reformate of increased aromatic content,separating said reformate into a portion rich in aromatics and anon-aromatic portion, contacting said second liquid fraction with acracking catalyst under cracking conditions to produce a crackedproduct, separating the cracked product into a C3-C4 olefin-containingfraction and a cracked naphtha fraction, subjecting said CTC.,olen-containing fraction to polymerization conditions in the presence ofa polymerization catalyst to produce a normally liquid polymer,combining said normally liquid polymer and non-aromatic said portion,contacting the combined stream with a hyclrogenation catalyst in thepresence of 5,000-l5,000 s.c.f. hydrogen per barrel under saturationconditions, fractionating the hydrogenation product into a liquidfraction boiling below about 200 F. and a jet fuel fraction boilingabove about 200 F. and combining said fraction boiling below about 200F. with said portion rich in aromatics to produce a motor fuel of highoctane number.

References Cited in the file of this patent UNITED STATES PATENTS

1. A PROCESS FOR THE PRODUCTION OF AN IMPROVED JET FUEL WHICH COMPRISESFRACTIONATING A CRUDE PETROLEUM INTO A FIRST LIQUID FRACTION HAVING ADISTILLATION END JPOINT OF ABOUT 390*F. AND A SECOND LIQUID FRACTIONBOILING WITHIN THE RANGE OF ABOUT 390-760*F., REFORMING SAID FIRSTLIQUID FRACTION TO PRODUCE A REFORMATE OF INCREASED AROMATIC CONTENT,SEPARATING SAID REFORMATE INTO A PORTION RICH IN AROMATICS AND ANON-AROMATIC PORTION, CONTACTING SAID SECOND LIQUID FRACTION WITH ACRACKING CATALYST UNDER CRACKING CONDITIONS TO PRODUCE A CRACKEDPRODUCT, SEPARATING THE CRACKED PRODUCT INTO A C3-C4 OLEFIN-CONTAININGFRACTION AND A CRACKED NAPHTHA FRACTION, SUBJECTING SAID C3-C4OLEFIN-CONTAINING FRACTION TO POLYMERIZATION CONDITIONS IN THE PRESENCEOF A POLYMERIZATION CATALYST TO PRODUCE A NORMALLYLIQUID POLYMER,COMBINING SAID NORMALLY LIQUID POLYMER AND SAID NON-AROMATIC PORTION,CONTACTING THE COMBINED STEAM WITH A HYDROGENATION CATALYST IN THEPRESENCE OF 5,000-15,000 S.C.F. HYDROGEN PER BARREL UNDER SATURATIONCONDITIONS AND RECOVERING A HYDROCARBON FRACTION BOILING IN THE JET FUELRANGE FROM THE HYDROGENATION PRODUCT.